The .AUTOSUBTITLE command causes DSR to use .HEADER LEVEL titles
    for running-head subtitles. Subtitles therefore can change
    according to the section title that applies to a given page.
    The .NO AUTOSUBTITLE command cancels the .AUTOSUBTITLE function.
    (See .HEADERS ON, .SUBTITLE, and .HEADER LEVEL.)

    Formats

      .AUTOSUBTITLE  [[+/-]n]

      .NO AUTOSUBTITLE

    Abreviated formats

      .AST  [[+/-]n]

      .NAST